Fatigue is a subjective feeling of tiredness that has a gradual onset. Unlike weakness, fatigue can be alleviated by periods of rest. Fatigue can have physical or mental causes. Physical fatigue is the transient inability of a muscle to maintain optimal physical performance, and is made more severe by intense physical exercise. Mental fatigue is a transient decrease in maximal cognitive performance resulting from prolonged periods of cognitive activity. It can manifest as somnolence, lethargy, or directed attention fatigue.
|Synonyms||Exhaustion, tiredness, languidness, languor, lassitude, listlessness|
|Sleeping students. Occupations that require an individual to work long hours or stay up overnight can lead to fatigue.|
Medically, fatigue is a non-specific symptom, which means that it has many possible causes and accompanies many different conditions. Fatigue is considered a symptom, rather than a sign, because it is a subjective feeling reported by the patient, rather than an objective one that can be observed by others. Fatigue and 'feelings of fatigue' are often confused.
Physical fatigue, or muscle fatigue, is the temporary physical inability of a muscle to perform optimally. The onset of muscle fatigue during physical activity is gradual, and depends upon an individual's level of physical fitness, and also upon other factors, such as sleep deprivation and overall health. It can be reversed by rest. Physical fatigue can be caused by a lack of energy in the muscle, by a decrease of the efficiency of the neuromuscular junction or by a reduction of the drive originating from the central nervous system. The central component of fatigue is triggered by an increase of the level of serotonin in the central nervous system. During motor activity, serotonin released in synapses that contact motoneurons promotes muscle contraction. During high level of motor activity, the amount of serotonin released increases and a spillover occurs. Serotonin binds to extrasynaptic receptors located on the axon initial segment of motoneurons with the result that nerve impulse initiation and thereby muscle contraction are inhibited.
Muscle strength testing can be used to determine the presence of a neuromuscular disease, but cannot determine its cause. Additional testing, such as electromyography, can provide diagnostic information, but information gained from muscle strength testing alone is not enough to diagnose most neuromuscular disorders.
People with multiple sclerosis experience a form of overwhelming lassitude or tiredness that can occur at any time of the day, for any duration, and that does not necessarily recur in a recognizable pattern for any given patient, referred to as "neurological fatigue".
Mental fatigue is a temporary inability to maintain optimal cognitive performance. The onset of mental fatigue during any cognitive activity is gradual, and depends upon an individual's cognitive ability, and also upon other factors, such as sleep deprivation and overall health. Mental fatigue has also been shown to decrease physical performance. It can manifest as somnolence, lethargy, or directed attention fatigue. Decreased attention may also be described as a more or less decreased level of consciousness. In any case, this can be dangerous when performing tasks that require constant concentration, such as operating large vehicles. For instance, a person who is sufficiently somnolent may experience microsleep. However, objective cognitive testing can be used to differentiate the neurocognitive deficits of brain disease from those attributable to tiredness.
Fatigue impacts a driver's reaction time, awareness of hazards around them and their attention. Drowsy drivers are three times more likely to be involved in a car crash and if they are awake over 20 hours, is the equivalent of driving with a blood-alcohol concentration level of 0.08%.
Fatigue is a normal result of working, mental stress, overstimulation and understimulation, jet lag or active recreation, depression, boredom, disease, and lack of sleep. It may also have chemical causes, such as poisoning, low blood sugar, or mineral or vitamin deficiencies. Chronic blood loss frequently results in fatigue, as do other conditions that cause anemia. Fatigue is different from drowsiness, where a patient feels that sleep is required. Fatigue is a normal response to physical exertion or stress, but can also be a sign of a physical disorder.
Prolonged fatigue is a self-reported, persistent (constant) fatigue lasting at least one month. Chronic fatigue is a self-reported fatigue lasting at least six consecutive months. Chronic fatigue may be either persistent or relapsing. Chronic fatigue is a symptom of many diseases and conditions. Some major categories of conditions that feature fatigue include:
- Autoimmune diseases such as celiac disease, lupus, multiple sclerosis, myasthenia gravis, Sjögren's syndrome, and spondyloarthropathy
- Blood disorders such as anemia and hemochromatosis
- Cancer, in which case it is called cancer fatigue
- Chronic fatigue syndrome (CFS)
- Drug abuse including alcohol abuse
- Depression and other mental disorders that feature depressed mood
- Developmental disorders such as autism spectrum disorder
- Eating disorders, which can produce fatigue due to inadequate nutrition
- Endocrine diseases like diabetes mellitus and hypothyroidism
- Gulf War syndrome
- Heart disease
- Inborn errors of metabolism such as fructose malabsorption.
- Infectious diseases such as infectious mononucleosis.
- Irritable bowel syndrome
- Leukemia or lymphoma
- Liver failure
- Lyme disease
- Neurological disorders such as narcolepsy, Parkinson's disease and post-concussion syndrome
- Physical trauma and other pain-causing conditions, such as arthritis
- Sleep deprivation or sleep disorders
- Spring fever
- Thyroid diseases
- Uremia, which is caused by kidney disease
Fatigue may also be a side effect of certain medications (e.g., lithium salts, ciprofloxacin); beta blockers, which can induce exercise intolerance; and many cancer treatments, particularly chemotherapy and radiotherapy.
One study concluded about 50% of people who have fatigue receive a diagnosis that could explain the fatigue after a year with the condition. In those people who have a possible diagnosis, musculoskeletal (19.4%) and psychological problems (16.5%) are the most common. Definitive physical conditions were only found in 8.2% of cases.
If a person with fatigue decides to seek medical advice, the overall goal is to identify and rule out any treatable conditions. This is done by considering the person's medical history, any other symptoms that are present, and evaluating of the qualities of the fatigue itself. The affected person may be able to identify patterns to the fatigue, such as being more tired at certain times of day, whether fatigue increases throughout the day, and whether fatigue is reduced after taking a nap.
Because disrupted sleep is a significant contributor to fatigue, a diagnostic evaluation considers the quality of sleep, the emotional state of the person, sleep pattern, and stress level. The amount of sleep, the hours that are set aside for sleep, and the number of times that a person awakens during the night are important. A sleep study may be ordered to rule out a sleep disorder.
Depression and other psychological conditions can produce fatigue, so people who report fatigue are routinely screened for these conditions, along with drug abuse, poor diet, and lack of physical exercise, which paradoxically increases fatigue.
Basic medical tests may be performed to rule out common causes of fatigue. These include blood tests to check for infection or anemia, a urinalysis to look for signs of liver disease or diabetes mellitus, and other tests to check for kidney and liver function, such as a comprehensive metabolic panel. Other tests may be chosen depending on the patient's social history, such as an HIV test or pregnancy test.
Comparison with sleepinessEdit
Fatigue is generally considered a more long-term condition than sleepiness (somnolence). Although sleepiness can be a symptom of medical issues, it usually results from lack of restful sleep, or a lack of stimulation. Chronic fatigue, on the other hand, is a symptom of a greater medical problem in most cases. It manifests in mental or physical weariness and inability to complete tasks at normal performance. Both are often used interchangeably and even categorized under the description of 'being tired.' Fatigue is often described as an uncomfortable tiredness, whereas sleepiness is comfortable and inviting.
Fatigue can be quantitatively measured. Devices to measure medical fatigue have been developed by Japanese companies, among them Nintendo. Nevertheless such devices are not in common use outside Japan.
- Gandevia, S. C. (February 1992). "Some central and peripheral factors affecting human motoneuronal output in neuromuscular fatigue". Sports Medicine. 13 (2): 93–8. doi:10.2165/00007256-199213020-00004. PMID 1561512.
- Hagberg, M. (July 1981). "Muscular endurance and surface electromyogram in isometric and dynamic exercise". Journal of Applied Physiology. 51 (1): 1–7. doi:10.1152/jappl.1918.104.22.168. PMID 7263402.
- Hawley, John A.; Reilly, Thomas (1997). "Fatigue revisited". Journal of Sports Sciences. 15 (3): 245–6. doi:10.1080/026404197367245. PMID 9232549.
- Marcora, Samuele M.; Staiano, Walter; Manning, Victoria (January 2009). "Mental fatigue impairs physical performance in humans". Journal of Applied Physiology. 106 (3): 857–64. CiteSeerX 10.1.1.557.3566. doi:10.1152/japplphysiol.91324.2008. PMID 19131473.
- Berrios, G. E. (1990). "Feelings of fatigue and psychopathology: a conceptual history". Comprehensive Psychiatry. 31 (2): 140–51. doi:10.1016/0010-440X(90)90018-N. PMID 2178863.
- "Weakness and fatigue". Healthwise Inc. Retrieved 2 January 2013.
- Gandevia, S. C. (October 2001). "Spinal and supraspinal factors in human muscle fatigue". Physiological Reviews. 81 (4): 1725–89. doi:10.1152/physrev.2001.81.4.1725. PMID 11581501.
- Davis, J. Mark; Anderson, Nathan L.; Welsh, Ralph S. (August 2000). "Serotonin and central nervous system fatigue: nutritional considerations" (PDF). The American Journal of Clinical Nutrition. 72 (2 Suppl): 573S–8S. doi:10.1093/ajcn/72.2.573S. PMID 10919962.
- Perrier, Jean-François; Delgado-Lezama, Rodolfo (August 2005). "Synaptic Release of Serotonin Induced by Stimulation of the Raphe Nucleus Promotes Plateau Potentials in Spinal Motoneurons of the Adult Turtle" (PDF). The Journal of Neuroscience. 25 (35): 7993–9. doi:10.1523/JNEUROSCI.1957-05.2005. PMID 16135756.
- Cotel, Florence; Exley, Richard; Stephanie J., Cragg; Perrier, Jean-François (March 2013). "Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation" (PDF). Proceedings of the National Academy of Sciences of the United States of America. 110 (12): 4774–9. doi:10.1073/pnas.1216150110. PMC 3607056. PMID 23487756.
- Enoka, Roger M.; Duchateau, Jacques (January 2008). "Muscle fatigue: what, why and how it influences muscle function". The Journal of Physiology. 586 (1): 11–23. doi:10.1113/jphysiol.2007.139477. PMC 2375565. PMID 17702815.
- Comi, G.; Leocani, L.; Rossi, P.; Colombo, B. (March 2001). "Physiopathology and treatment of fatigue in multiple sclerosis". Journal of Neurology. 248 (3): 174–9. doi:10.1007/s004150170222. PMID 11355149.
- Mills, Roger J.; Young, Carolyn A.; Pallant, Julie F.; Tennant, Alan (February 2010). "Development of a patient reported outcome scale for fatigue in multiple sclerosis: The Neurological Fatigue Index (NFI-MS)". Health and Quality of Life Outcomes. 8: 22. doi:10.1186/1477-7525-8-22. PMC 2834659. PMID 20152031.
- Giannini, A.J. (1991). "Fatigue, Chronic". In Taylor, Robert B. Difficult Diagnosis 2. Philadelphia: W.B. Saunders Co. p. 156. ISBN 978-0-7216-3481-4. OCLC 954530793.
- "Drowsy Driving is Impaired Driving". National Safety Council. Retrieved 31 January 2019.
- Fukuda, Keiji; Straus, Stephen E.; Hickie, Ian; Sharpe, Michael C.; Dobbins, James G.; Komaroff, Anthony (December 1994). "The Chronic Fatigue Syndrome: A Comprehensive Approach to Its Definition and Study" (PDF). Annals of Internal Medicine. 121 (12): 953–9. doi:10.7326/0003-4819-121-12-199412150-00009. PMID 7978722.
- Avellaneda Fernández, Alfredo; et al. (October 2009). "Chronic fatigue syndrome: aetiology, diagnosis and treatment". BMC Psychiatry. 9 (Suppl 1): S1. doi:10.1186/1471-244X-9-S1-S1. PMC 2766938. PMID 19857242.
- Whitehead, W. E.; Palsson, O.; Jones, K. R. (April 2002). "Systematic review of the comorbidity of irritable bowel syndrome with other disorders: What are the causes and implications?". Gastroenterology. 122 (4): 1140–56. doi:10.1053/gast.2002.32392. PMID 11910364.
- Gibson, P. R.; Newnham, E.; Barrett, J. S.; Shepherd, S. J.; Muir, J. G. (November 2006). "Review article: Fructose malabsorption and the bigger picture". Alimentary Pharmacology & Therapeutics. 25 (4): 349–63. doi:10.1111/j.1365-2036.2006.03186.x. PMID 17217453.
- Nijrolder, Iris; van der Windt, Daniëlle; de Vries, Henk; van der Horst, Henriëtte (November 2009). "Diagnoses during follow-up of patients presenting with fatigue in primary care". Canadian Medical Association Journal. 181 (10): 683–7. doi:10.1503/cmaj.090647. PMC 2774363. PMID 19858240.
- Davis, Charles Patrick (11 September 2017). Doerr, Steven, ed. "Fatigue". eMedicineHealth. Archived from the original on 7 March 2010.
- Shen, Jianhua; Barbera, Joseph; Shapiro, Colin M. (February 2006). "Distinguishing sleepiness and fatigue: focus on definition and measurement". Sleep Medicine Reviews. 10 (1): 63–76. doi:10.1016/j.smrv.2005.05.004. PMID 16376590.
- Hoddes, E.; Zarcone, V.; Smythe, H.; Phillips, R.; Dement, W. C. (July 1973). "Quantification of Sleepiness: A New Approach". Psychophysiology. 10 (4): 431–6. doi:10.1111/j.1469-8986.1973.tb00801.x. PMID 4719486.
- Mayou, Richard (January 1999). "Chronic fatigue and its syndromes". The BMJ. 318 (7176): 133A. doi:10.1136/bmj.318.7176.133a. PMC 1114599. PMID 9880310.
- "Nintendo's first health care device will be sleep and fatigue tracker". The Japan Times. Reuters. 30 October 2014. Retrieved 29 June 2017.
- Danish edition: Træthedssamfundet. Møller, 2012, ISBN 9788799404377.
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- Italian editions : La società della stanchezza. nottetempo, 2012, ISBN 978-88-7452-345-0.
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